1. Field of the Invention
The present invention relates to a technique for cleaning a semiconductor substrate.
2. Description of the Related Art
Formation of a through-hole or an interconnect trench in a manufacturing process for LSI is generally carried out using a lithography technique and a cleaning technique. A typical process includes steps of: forming a resist pattern on an insulating layer and subsequently dry-etching the insulating layer using the resist pattern as a mask; and then removing the resist pattern by ashing the resist pattern and spraying a stripping solution onto the resist pattern. Further, a rinse is then carried out using a selected solvent. The rinse is carried out to remove residual materials resulting from the resist removal in order to keep the substrate surface clean and thus the rinse is the important processing that affects the reliability of the resultant semiconductor devices.
Following technologies related to a rinse step are conventionally known.
JP-A-H11-214,350 discloses a typical batch type rinse technique. The technique will be described below with reference to FIG. 12. As shown in FIG. 12, an apparatus for processing and drying of substrate comprises a processing bath 103 containing therein warm pure water (at a temperature of approximately 60 degree. C.) as a processing solution 101. The apparatus further comprises a conveyer (not shown) for holding and conveying a carrier 107 on which a plurality of silicon wafers 105 are vertically mounted. The conveyer transfers the individual silicon wafers 105 into the processing solution 101 to dip the wafers into the solution and then retrieves the wafers therefrom.
In the apparatus for processing and drying of substrate, when the carrier 107 holding the silicon wafers 105 is lowered as indicated by an arrow Z1 upon actuation of the aforementioned conveyer, the individual silicon wafers 105 are dipped into the processing solution 101. Dipping the silicon wafers 105 into the processing solution 101 rinses the wafers. Upon completion of the rinse, the aforementioned conveyer removes from the solution 101 the carrier 107 in the direction indicated by an arrow Z2 at a relatively low speed (e.g., 1 mm/sec.). As is apparent from FIG. 13, removing the wafers at the relatively low speed removes from the surface of the silicon wafer 105 the processing solution adhered to the surface thereof, so that the solution adhered thereto is pulled back by the surface tension of the solution to the side of the processing solution 101 within a processing bath 103 (pulling force is indicated by an arrow p1). As such, removal of the wafers from the solution simultaneously terminates the drying of the silicon wafers 105.
JP-A-H11-204,491 discloses another bath-type cleaning technique. The publication discloses a technique for rinsing a substrate with ultra pure water and then drying the substrate with isopropyl alcohol (hereinafter abbreviated as IPA).
Although the above described techniques for rinsing wafers in a Batch Wafer Processing Equipment, various other techniques for rinsing wafers in a Single Wafer Processing Equipment. JP-A-2000-58,498 discloses a technique for rinsing wafers in a Batch Wafer Processing Equipment. The publication describes a method for rinsing a substrate with ultra pure water and spraying isopropyl alcohol (IPA) onto a surface of the substrate to dry the surface thereof.
As described in the above-listed publications, a rinse step is performed using an ultra pure water after a wet etch step. In some cases, as described in JP-A-H11-204,491 and JP-A-2000-58,498, a rinse step is performed using an organic solvent such as IPA in addition to ultra pure water. However, in the latter case, the organic solvent is used only in a dry step after the rinse step is performed using ultra pure water, meaning that both the former and latter cases employ the ultra pure water to rinse a substrate.
The inventors of the present invention have found that when a semiconductor substrate is rinsed with an ultra pure water, the semiconductor substrate is charged with an electrical charge because of high electrical resistivity of the ultra pure water and thus a metal film and/or an insulating film formed on the substrate are damaged.
Further, rinsing a substrate with an ultra pure water takes a long period of time to remove residual materials from the surface of substrate and dry the substrate after the rinsing, thereby decreasing the throughput of substrate.
Problems specifically related to the technique for rinsing wafers in a Batch Wafer Processing Equipment and the technique for rinsing wafers in a Single Wafer Processing Equipment are described below. That is, rinsing wafers in a Batch Wafer Processing Equipment requires a significant amount of rinse agent, thereby increasing production cost and environmental load. Moreover, rinsing wafers with an ultra pure water in a Single Wafer Processing Equipment further increases potential of charging-up of the substrate surface by the friction between the ultra pure water and the substrate, thereby decreasing the production yield.
In consideration of the above-stated problems found in the conventional techniques, the present invention has been conceived to solve those problems. Therefore, it is an object of the present invention to prevent damages that are applied during a cleaning step to a metal film and an insulating film formed on the substrate. It is another object of the present invention to provide a method for efficiently removing residual materials from the surface of substrate and after cleaning of the substrate, efficiently drying the substrate, thereby allowing increase in the throughput of substrate. It is yet another object of the invention to reduce production cost and environmental load in a cleaning step while increasing production yield.